A Steric Interlocked Phosphorescent Iridium(III) Complex Toward Ultrapure Green Electroluminescence

The development of phosphorescent materials with ultrapure emission is of great significance for wide‐color‐gamut organic light‐emitting diodes (OLEDs). Herein, a ligand steric interlocking strategy is introduced to achieve the narrowband emission of phosphorescent Ir(III) complexes. The steric interlocking effect contributed by the short distance between ligands leads to enhanced rigidity, and suppresses the high‐frequency vibrations of o ICz‐Ir. In this context, o ICz‐Ir exhibits an ultrapure green phosphorescence with a small full width at half maximum (FWHM) of 23 nm peaking at 521 nm in solution. Furthermore, the o ICz‐Ir‐based OLED achieves a maximum external quantum efficiency (EQE max ) of 18.9%, an excellent color purity with Commission Internationale de L'Eclairage coordinate y (CIE y ) of 0.69, making it the purest green bottom‐emitting phosphorescent OLEDs. Meanwhile, with o ICz‐Ir as the sensitizer, a phosphorescence sensitized fluorescent OLED shows an excellent EQE max of 31.1% with the CIE y of 0.7.